“Over half of U.S. adults surveyed said that it’s very inappropriate, somewhat appropriate, or were uncertain whether it’s appropriate for their child to set boundaries for their interactions” is a reasonable-sounding statement, too; it’s plausible, applies to children of all ages (below or beyond age 25!), and is demonstrably an aspect of culture represented by media and other ephemera.

The position itself is, of course, completely unreasonable — boundaries are never inappropriate to consider (and to contrast with the parent’s boundaries about immediate versus deferred conversations in unsafe circumstances, the child’s age and cognitive ability to assess risk, and so on), no matter how uncomfortable it is to teach a child about boundaries by honoring one they’ve presented one! — but that intolerance is presented in such a reasonable guise, with a tone of majority support to quash any brief qualms, that it causes many to overlook its true nature.

See also “pleasant”, as in “Pleasantville”.